The Application Of Local Composition Model In Electrolyte Solution For Salt-Water System

The applicability of the local composition theory for electrolyte solution to salt-water system was investigated on the basis of MatLab in this work. The programs of thermodynamical model for the calculations of solvent-salt interaction parameters and salt-salt interaction parameters in the model were established; the functions of"fminsearch"and"fsolve"in MatLab were used in program to regress parameters and solve equations; utilizing the osmotic coefficients, the solvent-salt interaction parameters in binary salt-water systems according to NaNO3-H2O, KNO3-H2O, Mg(NO3)2-H2O, NaCl-H2O, KCl-H2O and MgCl2-H2O were obtained in a more wider range of concentration; utilizing the solubilities, the salt-salt interaction parameters in ternary salt-water systems according to Na+,K+//NO3--H2O , Na+,Mg²⁺//NO3--H2O , K+,Mg²⁺//NO3 - -H2O , Na+,K+//Cl--H2O ,Na+,Mg²⁺//Cl--H2O , K+,Mg²⁺//Cl--H2O , Na+//Cl-,NO3--H2O , K+//Cl-,NO3--H2O ,Mg²⁺//Cl-,NO3--H2O were obtained; the deviation was calculated and discussed; the method for predicting phase equilibrium of quaternary salt-water system was suggested.The research shows: the local composition theory of electrolyte solution is suitable for the salt-water system in which the ionic strength is lower and the size of ion is smaller.